DESCRIPTION (Applicant's abstract): This project proposes the use of multiple physiological methods to: 1) develop an objective measure of trait-like patterns of affective responding, and 2) to better understand the relations between individual differences in the time course of emotional reactions, and the neural substrates underlying emotional experience. Despite the growing body of emotion research, few objective, non-self-report induces of emotional experience exist, and very little work has been done examining the temporal course of responses to an emotion elicitor. The time course of emotions may be a very important variable in understanding individual differences in affective style. For example, individuals who experience negative emotions longer may be more likely to become anxious or depressed. To address the first goal, developing an objective measure of trait affective responding, the stability of the emotion-modulated startle response will be assessed to determine whether this paradigm shows suitable reliability for use as a trait -like index. The second goal, understanding the chronometry of emotions, will use subjects with extreme asymmetry of frontal EEG activation (shown previously to be related to state and trait affect) to examine individual differences in the time course of cortical and subcortical brain activation (measured with FMRl) in response to affectively-laden pictures.